John Orcutt N305JK

[John Orcutt]

Hello fellow Mooney enthusiast! This is my first time on this chat site. I have a 305 Mooney rocket and I am wondering if anyone else has experienced a coking issue with their turbo charger? I have approximately 1600 hrs on my current rocket. I replaced the engine approximately 650 hours ago. Within the last eight months I’ve had two nearly catastrophic issues with my turbo charger. Coking has occurred twice in 8-9 months blocking the Oil return/scavenge outlet. My last flight of approximately 10 minutes resulted in losing approximately 7 quarts of oil burnt through the turbo charger. Fortunately, The flight was a short one. I understand from my mechanic that there is a service bulletin regarding this issue on the Mooney rockets. It should be checked every 100 hours. It has not occurred during the prior 1600 hrs of Rocket time. My mechanics and I are trying to find the reason and a solution. 
I would appreciate any thoughts or if anyone else has had this experience. If you own a Rocket, be sure to check for this issue. It takes only several minutes to burn through your oil supply before a catastrophic event could occur. I’d appreciate any and all responses.

Thanks, John O

[FloridaMan]

What oil are you running? Do you know where I can find this SB?

[PhilB]

Are you running mineral oil? You gotta check the engine manufacturer's service instructions about what oils are allowed. Mineral oil cokes up quick at the temps in the turbocharger.


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[LANCECASPER]

Call Rocket Engineering in Spokane, WA. (509) 535-6445 They still offer some support.

[Mooney_Allegro]

Hello John,

Your issue is eye opening and very scary!   I wish I could help, but I'm not a mechanic.  I'm operating two turbochargers on an Acclaim with well over 900 hours and have not had any issues with them.....yet.  Please keep us informed of your outcome so we can all learn.  I'm sorry to hear of your issue.  

David

[carusoam]

welcome aboard John…

 

There is a ton of information around here discussing the best way to cool the TCs prior to shut down…

And it clearly isn’t idling before shutting down…

See if you can find those conversations…

Let me invite a few people that have been part of this conversation in the past…. @aviatoreb, @gsxrpilot, and @Yooper Rocketman…

There are thousands  of MSers with turbo experience… none of them are currently reporting coking issues as a regular occurrence…

So… let’s find out what you are doing differently… or what you can do differently…

 

Be ready to answer a lot of questions while we try to get to know you, and your machine details, a little better… 

 

How much time do you have on the engine, turbo, and scavenger pump?

Best regards,

-a-

[aviatoreb]

On 9/21/2021 at 2:07 PM, John Orcutt said:

Hello fellow Mooney enthusiast! This is my first time on this chat site. I have a 305 Mooney rocket and I am wondering if anyone else has experienced a coking issue with their turbo charger? I have approximately 1600 hrs on my current rocket. I replaced the engine approximately 650 hours ago. Within the last eight months I’ve had two nearly catastrophic issues with my turbo charger. Coking has occurred twice in 8-9 months blocking the Oil return/scavenge outlet. My last flight of approximately 10 minutes resulted in losing approximately 7 quarts of oil burnt through the turbo charger. Fortunately, The flight was a short one. I understand from my mechanic that there is a service bulletin regarding this issue on the Mooney rockets. It should be checked every 100 hours. It has not occurred during the prior 1600 hrs of Rocket time. My mechanics and I are trying to find the reason and a solution. 
I would appreciate any thoughts or if anyone else has had this experience. If you own a Rocket, be sure to check for this issue. It takes only several minutes to burn through your oil supply before a catastrophic event could occur. I’d appreciate any and all responses.

Thanks, John O

I have not ever experienced this problem you are describing.  I do not do a turbo cool down period after flight and I can view on my downloaded JPI data that the coolest time of the turbo is immediately upon touch down following approach to landing that is usually at low power with good airflow and low power demand.  After touch down, during taxi to parking the turbo heats up slightly and no amount of idling sitting at the parking spot will cause the turbo to cool down to where it was upon touch down.

I am very curious what you learn is causing your coking issue since I do have the same model as you and in case it ever happens to me that I end up in the same situation as you.

And if you would point us to the SB please.

Erik

[GeeBee]

Insufficient lubrication

Excessive lubrication

Wrong oil

Excessive rich mixture

Excessive TIT

Insufficient turbo insulation

[Will.iam]

1 hour ago, GeeBee said:

Insufficient lubrication

Excessive lubrication

Wrong oil

Excessive rich mixture

Excessive TIT

Insufficient turbo insulation

I understand how all those would cause coking but the excessive lubrication and excessive  rich mixture. When i have ever put full rich mixture on the ground idling, my turbo TIT goes way down below 700degrees in fact. How does excessive rich mixture cause coking? 

[Guest]

I’ve never worked on a Rocket, does it use check valves in the turbocharger oil system?  Is it possible that a check valve is dirty or partially clogged.  A partially blocked hose or weak/worn scavenge oil pump also come to mind.

Clarence

[GeeBee]

2 hours ago, Will.iam said:

I understand how all those would cause coking but the excessive lubrication and excessive  rich mixture. When i have ever put full rich mixture on the ground idling, my turbo TIT goes way down below 700degrees in fact. How does excessive rich mixture cause coking? 

For the same reason excessive rich mixture will foul plugs and valves, especially at idle. You should have a mixture at idle that barely keeps the engine running.

The rich mixture is heavily laden with deposits which will not burn off due to low temps. Since you are at idle the only way to minimize them is to minimize the fuel. Once you advance the throttle, those deposits may not clear and bake on....coking which is hardened carbon deposits. 

See this all the time on diesels with failed injectors. As a matter of fact I just lost a VW Jetta diesel turbo that was all coked up from a rich injector. New turbo was more than the car was worth. Loved that car too.

[Yooper Rocketman]

I flew my Rocket for 1800 hours, after buying it with 300 hours since new (the conversion and the engine).  I agree with @aviatoreb.  I stopped doing the "cool down" shortly after buying my plane, after reviewing several articles written by knowledgeable turbo engine aircraft people.  I found the same thing as Erik; idling for cool down did the opposite of the desired result.  It brought the oil and exhaust temps back up.  I never had any coking.  I have to wonder what oil you are using?  I used Aeroshell 100 (50 WT) the entire time, even in the winter (but flying out of a heated hangar and blocked off half the oil cooler for the winter).  I replaced one turbo at 1,100 hours, the second another 1,000 hours later (had over 2100 hours on the 1600 TBO engine when I overhauled it and sold it).  

There IS a check valve and scavenge pump in the turbo oil system.  With the turbo at the very bottom of the engine, it would probably be a good idea to inspect those two components for proper operation.  I would check your oil return line for any restriction as well.  I do believe if the scavenge pump fails you would pump the excess oil overboard into the exhaust fairly quickly. so not likely the problem.  I know of at least one pretty new Continental that did that on a Lancair IVP and resulted in an off airport landing in Colorado.

Tom

[carusoam]

@John Orcutt

Seeing if you are cruising by here….

There are a few interesting responses above…

Best regards,

-a-

[affricate]

20 hours ago, carusoam said:

@John Orcutt

Seeing if you are cruising by here….

There are a few interesting responses above…

Best regards,

-a-

I just read these responses to my friend @John Orcutt who's been on vacation for a week.

He kindly thanks everyone for their input, and he will update everyone this week.